Loose leaf binders having conventional metallic toggle ring mechanisms as a means for fastening the sheets within the binder are, of course, well known in the art. For certain uses such binders are more bulky and costly than necessary and file folders are frequently substituted therefor when relatively small number of sheets are to be bound. Accordingly, lightweight binders such as those shown in U.S. Pat. No. 2,133,069 to Williamson, No. 2,575,583 to Clarke et al, No. 2,289,949 to Wisdom and No. 2,445,671 to Johnson have been disclosed for such purposes. While these binders are characterized by economy of manufacture in that the covers are lightweight and the means by which sheets are fastened within the binder are integral with the covers, each has certain drawbacks. By way of example, the Wisdom binder requires twisting and bending of the disclosed fastening tongues. This cumbersome and tedious operation is required each time sheets are added or removed from the folder and with extended usage the tongues tend to become frayed and torn. In addition, these tongues tend to tear those portions of the loose leaf sheets adjacent the perforations thereof. In the Johnson patent only one end of a fastening strip is affixed to the binder cover, the free end having an enlarged head with foldable wings for threading through the holes of loose leaf sheets. The fastener strips being free at their outer ends do not provide binder loops or rings and the sheets are held loosely on each strip by the wing portions of the enlarged head. The Clarke binder employs a tongue which must be folded generally longitudinally each time a sheet is to be added to or removed from the binder, such folding necessarily fatigues the material forming the tongue and reduces the useful life of the binder. The Williamson binder requires the precise interfitting of the fastener tongue through a pair of narrow slits in the binder cover each time sheets are added or removed from the binder, such a practice being exacting and tedious.
Accordingly, it is a principal object of the present invention to provide a lightweight loose leaf ring binder type folder of unitary construction which overcomes the drawbacks of the prior art.
It is another object to provide such a folder which is economical to manufacture and effective in operation.
It is another object of the present invention to provide such folders which may be stacked in flat condition for compact storage, shipment and handling.
It is another object of the present invention to provide such a folder with sheet fastening means which is quickly and conveniently opened and closed for the addition to and removal of sheet material.